The transfer of thixotropic materials through a pipe, trough or other similar vessel frequently presents many unusual problems. The apparent viscosity of the thixotropic material can be greatly reduced by rapid stirring prior to the entry into the relative quiet of a vessel such as a pipe. If the force is sufficiently great, and residual turbulence from the rapid stirring still pronounced, the introduction of the material presents no unusual problems. However, if the pipe is long or if the diameter of the pipe is large, and it runs full, producing relatively low flow velocity, the viscosity of the thixotropic material can increase rapidly and plugging can occur. Attempts to force the material or plug through the pipe by increased pressure frequently fail. In many cases increased pressure results in removing additional liquid from the plug, thus making the movement of the plug even more difficult. The transfer of such material in a pipe is very difficult particularly if there is a rapid change in direction.
One of the areas where movement of thixotropic materials is particularly troublesome is in centrifuges. In my coexecuted application, Controlled Axial Movement in a Centrifuge, Ser. No. 392,011, filed Aug. 27, 1973, now abandoned, a method for axial moving thixotropic materials in a rotating centrifuge is disclosed. The rapidly stirred material in the centrifuge is removed from its rim by a scoop which forces the material towards the center of rotation. At this point the material must change direction to be removed from the centrifuge. Frequently, if a simple pipe is used, partial blocking of the axial pipe occurs. This further aggravates the problem as further movement is restricted. The net result is that additional material may build up and finally in many cases complete blockage results.